Magnetron sputtering is conventionally known as a means for film deposition on the surface of a substrate. In magnetron sputtering, there are used a target formed of a plate-like film-deposition material, a magnetic-field formation unit disposed behind the target, and a power source for applying sputtering voltage to the target. The power source generates glow discharge through application of the voltage, thereby ionizing an inert gas. Meanwhile, the magnetic-field formation unit forms a magnetic field in front of the target, thus allowing the ions to be irradiated directionally along the magnetic field. The magnetic field captures secondary electrons knocked off the target and promotes efficiently gas ionization, thereby allowing glow discharge to be maintained even at a low inert gas pressure to increase film deposition rate. This magnetron sputtering is utilized to restrain the secondary electrons and/or plasma from damaging the surface of the substrate, by means of the virtue of the magnetic field design thereof or utilized to control film characteristics through the plasma effect.
Furthermore, in recent years, in order to solve problems pertaining to contamination of the surface of the above targets, there have witnessed developments of dual magnetron sputtering (DMS) with use of a pair of targets as a cathode and anode of glow discharge, respectively. In DMS, disposition of, for instance, an AC power source between the pair of targets and alternate application of voltage between the targets is performed to thereby removing insulator generated on the surfaces of the targets, namely, self-cleaning; this allows film quality to be stabilized.
For instance, PTL 1 discloses a device that is schematically illustrated in FIG. 5. The device is provided with: a film deposition chamber 90 that accommodates a substrate 96; a first cathode 91 and a second cathode 92 that are disposed at opposite positions in the film deposition chamber 90; a film-deposition AC power source 94 connected to the cathodes 91, 92 to apply voltage alternately to the cathodes 91, 92; and not-graphically-shown magnetic-field formation magnets disposed behind respective cathodes 91, 92. The film deposition chamber 90 illustrated in the figure has a substantially octagonal cross-sectional shape, when viewed from above, in the center of which the substrate 96 is disposed. Each of the cathodes 91, 92 has a target formed of a film-deposition material and a cathode body retaining the target, disposed at mutually opposite positions in the vicinity of the side walls of the film deposition chamber 90 in such an attitude that the targets face the substrate 96. The substrate 96 is, therefore, disposed between the cathodes 91, 92.
The device disclosed in PTL 1, however, involves a problem of no ability of utilizing existing equipment for performing so-called pre-sputtering in advance of the start of film deposition.
The purposes of the pre-sputtering include: removal of impurities on the target surface (namely, self-cleaning); gradually increasing the target temperature to an appropriate temperature; and stabilization of the discharge state. The pre-sputtering can be achieved by eliciting discharge in each target in a state where the space between the substrate before film deposition and the targets is blocked by respective shutters. The shutters are opened upon the complement of the pre-sputtering, and film deposition on the substrate is initiated from that point onwards. In other words, the shutters are closed during pre-sputtering, thereby preventing unintended film deposition from being performed on the substrate by pre-sputtering.
The pre-sputtering, thus, requires an openable-closable shutter between the substrate and each target; however, if shutters, for instance, shutters 98 denoted by the two-dot chain lines in FIG. 5, were disposed between the cathodes 91, 92 and the substrate 96, the shutters would also block the targets of the cathodes 91, 92 from each other; this prevents the discharge between the cathodes 91, 92 from being carried out with use of the AC power source 94 for film deposition. Thus, there is inconvenience that the pre-sputtering of the targets cannot be carried out by use of the existing AC power source 94 for film deposition. Hence, this conventional device requires a dedicated power source for pre-sputtering, separate from the AC power source 94 for film deposition, to be prepared individually for the cathodes 91, 92. This involves significant increase in equipment costs.